Historically, manufacturing complex parts involved the fabrication of separate components and joining the components using fasteners or welding. This tends to be labor intensive and expensive. Thus, manufacturers have turned to adhesives. Examples of technology aimed toward meeting this need (and for which the present invention also finds utility for repair or replacement) include commonly owned co-pending applications hereby incorporated by reference: Ser. No. 10/051,417 (“Adhesively Bonded Valve Cover Cylinder Head Assembly”), wherein a valve cover is adhesively bonded to an engine with an epoxy resin; Ser. No. 09/922,030 (“Adhesively Bonded Water Conductor Assembly”), wherein a water conductor assembly outlet is adhesively bonded to a hose with an epoxy resin; U.S. Publication No. 03-0024768 (“Adhesively Bonded Oil Pan Assembly”), wherein an oil pan is adhesively bonded to an engine block with an epoxy resin; and Ser. No. 09/825,721 (“Adhesively Bonded Radiator Assembly”), wherein an end tank is adhesively bonded to a heat exchanger with an epoxy resin.
Among the advantages of being able to fabricate engine components of plastic are the resultant weight savings and the ability to fabricate intricately shaped components. Additionally it is also possible to integrate plural functions into a single component, heretofore served by separate components, thereby serving also to reduce overall part count for a vehicle. An example of one such structure is shown in commonly owned co-pending application U.S. Publication no. 04-000511 “Automotive Valve Cover With Integral Positive Crankcase Ventilation” (filed May 15, 2002), wherein a valve cover is adhesively bonded to an engine with an epoxy resin, hereby incorporated by reference. Examples of suitable joints include butt joints, lap joints, tongue in groove joint or the like. Further examples are illustrated in commonly owned, U.S. Pat. No. 6,543,404 (filed Apr. 4, 2001; entitled “Adhesively Bonded Engine Intake Manifold Assembly”) and U.S. Publication No. 02/0144808 (filed Apr. 4, 2001; entitled “Adhesively Bonded Radiator Assembly”).
Manufacturing techniques, such as those mentioned above, that use adhesives typically require less labor and are more cost effective. However, known adhesive systems present their own drawbacks. In particular, many traditional adhesives have difficultly in bonding different materials (e.g., plastic to metal, or two different types of plastic). Adhesives that form strong bonds require special handling, have short shelf life, or require special cure conditions.
Another shortcoming of traditional adhesive methods is the operational environment of the bond. For example, adhesives that bond plastic to plastic may form a strong bond at ambient conditions, but this bond may exhibit less integrity when subjected to elevated temperatures or elevated pressures. Moreover, the presence moisture, oils, lubricants, greases, solvents or the like may also compromise the bond.
Primers or adhesion promoters have been used in the past to treat a surface to promote bonding. To be useful, such adhesion promoters must be compatible with their corresponding adhesive as well as the underlying workpiece. Thus, many adhesion promoters suffer the same problems as their adhesive counterparts. Known adhesion promoters rely on large volumes of solvent that need to be disposed or may only work in conjunction with undesirable adhesives. Many adhesion promoter-adhesive systems require heat curing, which can be a time consuming process slowing the rate of production on a factory line.